command: don't allow adding local files on WIN32

There are no unix sockets on WIN32, and therefore no authentication.
WIN32 might have similar capabilities, but until we implement them,
disable that MPD feature.

src/playlist.c

@@ -517,6 +517,7 @@ static void clearPlayerQueue(void)
 	pc_cancel();
 }
 
+#ifndef WIN32
 enum playlist_result
 playlist_append_file(const char *path, int uid, unsigned *added_id)
 {
@@ -542,6 +543,7 @@ playlist_append_file(const char *path, int uid, unsigned *added_id)
 
 	return addSongToPlaylist(song, added_id);
 }
+#endif
 
 static struct song *
 song_by_url(const char *url)